Approximately 600,000 people in the United States experience sudden cardiac arrest (SCA) each year. SCA is the third leading cause of U.S. deaths. Active cooling after the start of cardiopulmonary resuscitation (CPR) can increase both heart and brain functional recovery with improved long-term survival. However, such cooling can be difficult to timely implement during CPR and when delayed may benefit only a subset of SCA patients. Unfortunately, no medications exist that improve long-term cardiac arrest survival. Proposed work develops first-of-their class biologic resuscitation agents that reproduce critical mechanisms of active cooling protection within minutes of intravenous delivery during CPR. The central hypothesis of this proposal is that rapid, specific and transient PTEN inhibition with onset of action within minutes of CPR and maintained for hours after CPR is highly protective of cardiac arrest survival. The cell permeable peptide TAT-PTEN9c reverses contractile failure (i.e. stunning) by enhancing glycolysis and activating pyruvate dehydrogenase (PDH). This enhanced glucose utilization decreases glucose diversion to sorbitol and attenuates additional cardiac injury related to sorbitol induced osmotic stress and compensatory taurine release. Nicotinamide (NAM, i.e. vitamin B3), a precursor of myocardial NAD+, is proposed to be a highly synergistic adjunct to TAT-PTEN9c for both NAD+-driven glucose utilization and NAD+-driven clearance of high myocardial sorbitol concentrations. The resulting improvement of cardiac function within hours after CPR supports increased tissue perfusion critical for 3-day neurologically intact survival. Three complementary aims using heart cell and isolated heart models of stunning, and determination of outcomes common to both mouse and human cardiac arrest, support the success of proposed work. Aim 1. Examine the efficacy of a novel TAT-fused peptide used in Aims #2 and #3 that specifically and rapidly blocks endogenous PTEN activity and reverses ischemic stunning in mouse cardiomyocytes. TAT-PTEN9c is a 20- amino acid cell-permeable peptide in which the TAT protein transduction domain is linked to the PTEN C- terminal 9 amino acids. Outcomes measured include return of contractility, protein kinase B (Akt) and GSK3? phosphorylation, and NAD+/NADH ratios and ATP contents. Aim 2. Determine the effect of TAT-PTEN9c and NAM supplementation on myocardial glucose and fat metabolism, pH, energetic recovery and cardiac function in the intact functioning rat heart model of global I/R. NMR-measured metabolic outcomes of glucose utilization (i.e. glycolysis and oxidation, versus diversion to sorbitol) will be linked to fat metabolism, improved contractile recovery and increased cardiac taurine preservation. Aim 3. Determine whether TAT-PTEN9C or NAM, given alone and in combination after CPR, significantly improves immediate cardiac recovery as well as 72 h neurologically intact survival using an established in vivo mouse SCA model. Blood markers of sorbitol-induced taurine release as well as NAM-enhanced sorbitol clearance will be characterized in the mouse and validated in a human SCA cohort of patients. A biologic agent that achieves cooling-like protection of critical organs such as the heart within minutes of intravenous delivery after CPR and immediately restores the cardiac function needed to support long-term neurologically intact survival would be a significant therapeutic advance in resuscitation medicine. Both TAT- fused peptides and the potentiating adjunct NAM are agents that could be rapidly advanced to large animal and human studies if shown to be effective in the proposed work. The use of blood taurine concentrations to predict outcome after both mouse and human cardiac arrest would be a major diagnostic advance.